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simulation.cpp
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simulation.cpp
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#include "simulation.h"
Simulation::Simulation(uint32_t w, uint32_t h, uint8_t scale, uint32_t count, uint8_t e, bool sort)
: width(w), height(h), w32((w+31)/32), xMax(w*256-1), yMax(h*256-1), particlecount(count),
scale(scale), elasticity(e), sort(sort), rand(true), particles{0}, bitmap{0}
{}
void Simulation::loadBackground(const uint32_t *bg) {
// Copy obstacles from image
for (int x = 0; x < width; ++x) {
for (int y = 0; y < height; ++y) {
// If non-black pixel, mark as obstacle
if (bg[y*width+x]!=0) {
setPixel(x, y);
}
}
}
}
void Simulation::loadParticles(const uint32_t *p, uint32_t count) {
if (count > SIM_MAX_PARTICLECOUNT) {
panic("Too many particles!\n");
}
particlecount = count;
for (int i = 0; i < particlecount; ++i) {
particles[i].x = 256*p[i*3]+128;
particles[i].y = 256*p[i*3+1]+128;
particles[i].color = p[i*3+2];
particles[i].vx = 0;
particles[i].vy = 0;
setPixel(particles[i].x/256, particles[i].y/256);
}
}
inline void Simulation::setPixel(uint32_t x, uint32_t y) {
bitmap[y] |= 0x80000000 >> x;
}
inline void Simulation::clearPixel(uint32_t x, uint32_t y) {
bitmap[y] &= ~(0x80000000 >> x);
}
inline bool Simulation::getPixel(uint32_t x, uint32_t y) const {
return bitmap[y]&(0x80000000 >> x);
}
// Comparsion functions are from Adafruit_PixelDust, adjusted for different type names
// Comparison functions for qsort(). Rather than using true position along
// acceleration vector (which would be computationally expensive), an 8-way
// approximation is 'good enough' and quick to compute. A separate optimized
// function is provided for each of the 8 directions.
static int __not_in_flash_func(compare0)(const void *a, const void *b) {
return ((particle_t *)b)->x - ((particle_t *)a)->x;
}
static int __not_in_flash_func(compare1)(const void *a, const void *b) {
return ((particle_t *)b)->x + ((particle_t *)b)->y - ((particle_t *)a)->x - ((particle_t *)a)->y;
}
static int __not_in_flash_func(compare2)(const void *a, const void *b) {
return ((particle_t *)b)->y - ((particle_t *)a)->y;
}
static int __not_in_flash_func(compare3)(const void *a, const void *b) {
return ((particle_t *)a)->x - ((particle_t *)a)->y - ((particle_t *)b)->x + ((particle_t *)b)->y;
}
static int __not_in_flash_func(compare4)(const void *a, const void *b) {
return ((particle_t *)a)->x - ((particle_t *)b)->x;
}
static int __not_in_flash_func(compare5)(const void *a, const void *b) {
return ((particle_t *)a)->x + ((particle_t *)a)->y - ((particle_t *)b)->x - ((particle_t *)b)->y;
}
static int __not_in_flash_func(compare6)(const void *a, const void *b) {
return ((particle_t *)a)->y - ((particle_t *)b)->y;
}
static int __not_in_flash_func(compare7)(const void *a, const void *b) {
return ((particle_t *)b)->x - ((particle_t *)b)->y - ((particle_t *)a)->x + ((particle_t *)a)->y;
}
static int (*compare[8])(const void *a, const void *b) = {
compare0, compare1, compare2, compare3,
compare4, compare5, compare6, compare7};
void __not_in_flash_func(Simulation::iterate)(int32_t ax, int32_t ay, int32_t az) {
// Scale down accelerometer inputs
// The inputs should be normalised already
ax = ax*scale / 256;
ay = ay*scale / 256;
int az2;
if (rand) {
az = abs(az*scale / (256*SIM_Z_NOISE_FACTOR)); // Used for random motion to topple stacks
az = (az >= (SIM_Z_NOISE_FACTOR / 2)) ? 1 : (SIM_Z_NOISE_FACTOR / 2 + 1) - az; // Limit and invert
// Subtract z motion factor, will be added back later with randomness
ax -= az;
ay -= az;
az2 = az * 2 + 1;
}
if (sort) {
// Sorting from Adafruit_PixelDust
int8_t q;
q = (int)(atan2(ay, ax) * 8.0 / M_PI); // -8 to +8
if (q >= 0)
q = (q + 1) / 2;
else
q = (q + 16) / 2;
if (q > 7)
q = 7;
// Sort particles by position, bottom-to-top
qsort(particles, particlecount, sizeof(particle_t), compare[q]);
}
int v2; // Squared velocity
float v; // Velocity
for (int i = 0; i < particlecount; ++i) {
// Apply acceleration
if (rand) {
particles[i].vx += ax + random() % az2;
particles[i].vy += ay + random() % az2;
} else {
particles[i].vx += ax;
particles[i].vy += ay;
}
// Limit total velocity to 256 to prevent particles from clipping through
// each other
// TODO: use fast inverse square root for this to make it faster
v2 = (int32_t)particles[i].vx*particles[i].vx+(int32_t)particles[i].vy*particles[i].vy;
if (v2 > 256*256) {
// Re-scale velocity while maintaining direction
//v = 256.0f*(1/sqrt((float)v2)); // Pre-calculate scaling factor for performance
//particles[i].vx = (int)((float)particles[i].vx*v);
//particles[i].vy = (int)((float)particles[i].vy*v);
v = sqrt((float)v2); // Pre-calculate scaling factor for performance
particles[i].vx = (int)(256.0*(float)particles[i].vx/v);
particles[i].vy = (int)(256.0*(float)particles[i].vy/v);
}
}
// Update positions of grains while checking for collisions
int32_t newx, newy;
int32_t oldidx, newidx, delta;
for (int i = 0; i < particlecount; ++i) {
// Apply velocity to get new proposed position
newx = particles[i].x + particles[i].vx;
newy = particles[i].y + particles[i].vy;
// First, check that we are still inside the simulation area
if (newx < 0) {
newx = 0;
BOUNCE(particles[i].vx);
} else if (newx > xMax) {
newx = xMax;
BOUNCE(particles[i].vx);
}
if (newy < 0) {
newy = 0;
BOUNCE(particles[i].vy);
} else if (newy > yMax) {
newy = yMax;
BOUNCE(particles[i].vy);
}
// Calculate "hash" of position in LED space
// Allows us to only need one comparison instead of several more computations
oldidx = (particles[i].y / 256)*width + (particles[i].x / 256);
newidx = (newy / 256)*width + (newx/256);
if ((oldidx != newidx) && getPixel(newx/256, newy/256)) {
// Tried to move to new pixel but it is already occupied
delta = abs(newidx-oldidx);
if (delta == 1) {
// Collision left or right, cancel x motion and bounce x
newx = particles[i].x;
BOUNCE(particles[i].vx);
} else if (delta == width) {
// Collision up or down, cancel y motion and bounce y
newy = particles[i].y;
BOUNCE(particles[i].vy);
} else {
// Diagonal collision, should be quite rare
// Try to skid along the "wall" with the faster axis first
if (abs(particles[i].vx) >= abs(particles[i].vy)) {
// X is faster (or equal)
if (!getPixel(newx/256, particles[i].y/256)) {
// Neighbour in x direction is free, take it and bounce y
newy = particles[i].y;
BOUNCE(particles[i].vy);
} else {
// Check if y is free
if (!getPixel(particles[i].x/256, newy/256)) {
// Neighbour in y direction is free, take it and bounce x
newx = particles[i].x;
BOUNCE(particles[i].vx);
} else {
// Nope, both occupied. Bounce x and y
newx = particles[i].x;
newy = particles[i].y;
BOUNCE(particles[i].vx);
BOUNCE(particles[i].vy);
}
}
} else {
// Y is faster
if (!getPixel(particles[i].x/256, newy/256)) {
// Neighbour in y direction is free, take it and bounce x
newx = particles[i].x;
BOUNCE(particles[i].vx);
} else {
// Check if x is free
if (!getPixel(newx/256, particles[i].y/256)) {
// Neighbour in x direction is free, take it and bounce y
newy = particles[i].y;
BOUNCE(particles[i].vy);
} else {
// Nope, both occupied. Bounce x and y
newx = particles[i].x;
newy = particles[i].y;
BOUNCE(particles[i].vx);
BOUNCE(particles[i].vy);
}
}
}
}
}
// Finally, update bitmap and stored position
clearPixel(particles[i].x/256, particles[i].y/256);
particles[i].x = newx;
particles[i].y = newy;
setPixel(newx/256, newy/256);
}
}
void Simulation::clearAll() {
// Clear entire bitmap
for (unsigned long & i : bitmap) {
i = 0;
}
}